Relevant Character Background
One of the reasons that most players do not give you verymuch background to work with, is that it doesn't have relevence to the plot. It will not help or hurt the Knight's chances of saving the princess if we learn that his father killed the family dog in front of the knight at the age of five- to 'toughen him up'. It doesn't increase the wizard's casting time if we learn that he taught himself to read with stolen books from a nearby monestary that he returned before dawn every day for fear of upseting the gods. So why should a player bother with this stuff. Because this stuff is cool, and as GM it is your job to prove it. Involve the Character's Backgrounds As the story gets bigger and the stakes get higher, slowly introduce the player's backgrounds into play. Not every player should be Luke Skywalker with the ultimate destiny of hero who will return the Jedi to their full glory. Some will be Han Solo, a character whose background causes problems in the middle of the story and complicates the central dilemma. Be creative and don't let one player hog the spotlight. Harry may have been the one to face off against Voldemort at the end of the first movie, but it was his friends skillfully included backgrounds that got him there in the first place. It may be best if the destined hero is an NPC and the some of the player characters are destined to protect that hero, and others have backgrounds that complicate that by bringing in additional requirements or adding villains or other problems. Look at “The Lord of the Rings” each character brings their own backgrounds to the table. Frodo must carry the weight. Sam defines himself as the loyal friend. Aragorn must take his place as King. Gandalf must orchestrate the political stage. Gimli and Legolas are defined by their rivalry. They all have parts to play that feature into the giant sweeping story, the story is not simply about Frodo, but how each other story contributes to Frodo's story. Character backgrounds as central plots Child of Destiny The character is born to their heroism or villainy. Luke Skywalker is the son of the villain and is destined to redeem his father and bring down the Empire he helped create. Creator of the Problem In “I am Legend” Richard Neville (played by Will Smith), may be partially responsible for creating the virus that has turned humanity into animalistic predators. The Hero by Tragedy Batman's parents were killed by criminals, and so he seeks to prevent other people from having to feel that pain. Backgrounds like this can be used to get characters into the center of all sorts of stories. Character backgrounds as complications Han Solo “I don’t have the money with me.” When the character has a monkey around their neck, such as a bounty on their head, an oath to a dying mother, a sick brother they have to look after, a debt that they have to pay, a loved one held hostage to ensure cooperation, the character will have to weigh everything they do against this factor. Sibling Rivalry/ Black Sheep Evil Twins, Villainous fathers, Conniving Stepmothers, and other treacherous, or simply competitive family members can add tension and interest to a story and make the fight personal. But if these characters are not central to the plot- a Jabba the Hutt, rather than a Darth Vader- they can drive the game by the way in which they complicate the plot for the characters. Tragedy as an Anti-Motivator Truman Burbank (Jim Carrey, in 'The Truman Show) had a boating accident orchestrated when he was very young in which his father appeared to die. This was done deliberately to prevent Truman from leaving the artificial island upon which he lived. These can make great tension builders for games. If your system doesn't have a system for it, you may consider offering some small offsetting advantage if a player is willing to start with such an anti-motivator that they must work to overcome. Character backgrounds as side-stories In 'Star Trek: Nemesis', the crew of the Star Ship U.S.S. Enterprise discovers B-4, Data's predecessor and thus mildly retarded older brother. B-4 features very mildly in the main story, but serves to add interest and stir up all sorts of questions. Lando Calrissian does the same thing in 'The Empire Strikes Back'. Luke and Yoda and Darth Vader are the primary plot, but his old friend and that old friend's betrayal all stir the pot and keep the plot moving. Character backgrounds as story depth A Character background doesn't need to feature in the story as an active element itself. We never meet the particular aliens who may or may not have abducted Randy Quaid's character in “Independence Day”. The event adds depth to the “Independence Day” story by telling us that the aliens have been preparing for their invasion for years. That event motivates him and is what helps him find the courage to make his kids proud and save the day, but that's all. And sometimes, that's enough. Character backgrounds as origins for a story The reason that Batman is Batman is because of how his parents died, but his background only occasionally serves as an active part of any Batman episode. His parent's murder is why he is Batman, and that is enough. Likewise, in most versions of the Joker's origin, the Joker is chemically burned or otherwise transformed into the Joker we know because of a chemical bath that the Joker took due to a run in with Batman early on. This is likewise rarely brought up, but in this case, the origin of Batman's prime villain is a part of his own background and obviously serves as motivation for both characters. This is true of many iconic villains. Spider-man created Venom inadvertently. Batman was likewise responsible for the creation of not just the Joker, but also Two-Face. Sabertooth is one of Wolverine's old teammates from their black-ops days.